The invention relates to heat exchangers, for a motor vehicle in particular.
It relates more particularly to a heat exchanger of the type comprising a bundle formed solely from flexible tubes made of plastics, as well as two end blocks joining these tubes.
Heat exchangers of this type are already known; they are also called xe2x80x9cfinless exchangersxe2x80x9d given that the bundle is formed solely from flexible tubes, also called capillary tubes. These may be of small diameter, typically of the order of 1 or 2 millimeters, and are usually produced by extrusion of a thermoplastic material, for example a polyamide.
Such heat exchangers can be used in the automobile industry, for example, to constitute a radiator for cooling the engine, a radiator for heating the passenger compartment, a cooler for the supercharger air or even a condenser of an air-conditioning circuit.
The advantage of these flexible tubes is that they make it possible to produce heat exchangers the tube bundle of which may exhibit particular shapes, including curved or arched shapes, so as to be able to be housed in an appropriate site in the motor vehicle. Moreover, they have the advantage of being lighter than the conventional heat exchangers with metal tubes, and they are moreover more resistant to impacts, because of their capability for deformation.
However, the production of such flexible-tube heat exchangers poses certain problems, given that it is not always possible to apply the usual techniques used in the manufacture of traditional heat exchangers with metal fins and tubes.
In the known heat exchangers with flexible tubes, the end blocks each comprise a manifold in the form of a plate provided with apertures individually accommodating the tubes of the bundle. This solution requires intricate assembly operations having regard to the fineness of the tubes and the large numbers of them.
Another problem relating to these known heat exchangers is due to the flexibility of the tubes. In fact, they have a tendency to move closer to one another thus forming an obstacle to the passage of the airflow that should sweep over the bundle. It is therefore necessary to provide means for holding the tubes spaced apart. The design of such spacer means poses numerous problems having regard to the fineness of the tubes and to the high number of them.
Another problem posed by these known heat exchangers lies in the supporting of the tubes which not only are flexible, but may also be of non-linear shapes.
The object of the invention is at least to partially mitigate the abovementioned drawbacks.
According to the present invention there is provided a heat exchanger, for a motor vehicle in particular, comprising a bundle formed solely from flexible tubes made of plastics, as well as two end blocks joining these tubes, characterized in that it comprises at least one spacer arranged at a chosen location between the end blocks and including apertures for the tubes to pass in order to provide support for the tubes with a chosen spacing or pitch.
It results therefrom that the tubes of the bundle are held spaced apart from one another, in such a way that the bundle can be correctly swept by a flow of air.
In one embodiment of the invention, each spacer is produced in the form of a generally flat plate provided with a plurality of individual holes spaced apart from one another and each suitable for being traversed by one tube of the tube bundle.
In another embodiment, each spacer is produced in the form of a generally flat plate provided with a plurality of oblong apertures spaced apart from one another and each suitable for being traversed by an aligned series of tubes of the bundle.
In this latter embodiment, the exchanger advantageously comprises at least one first spacer having first oblong apertures each suitable for being traversed by a row of tubes and at least one second spacer having second oblong apertures each suitable for being traversed by a column of tubes, the first oblong apertures and the second oblong apertures extending in orthogonal directions.
This second embodiment allows easier assembly than the preceding one, given that the tubes are introduced in aligned series and not individually.
According to another characteristic of the invention, each spacer is fixed between two crosspieces (also called cheeks) framing the tube bundle. These crosspieces contribute to supporting the bundle and to the rigidity of the assembly.
Advantageously, each spacer and the crosspieces are formed from a plastics material, particularly a thermoplastic material such as a polyamide.
Each spacer can be fixed to the crosspieces either by mechanical means, in particular by clipping, or else by bonding or by welding.
According to yet another characteristic of the invention, each spacer is placed in an orientation chosen in order to channel a flow of air sweeping the bundle of tubes.